The present invention relates to an oxide superconductor and a process for production thereof.
Conventional oxide superconductors include Bi--Sr--Ca--Cu--O system (hereinafter referred to as Bi system) oxide superconductors containing bismuth, strontium, calcium and copper as main elements, which were found in 1988 by Maeda, general researcher, and others of National Research Institute for Metals. These Bi system oxide superconductors have a problem in that it is difficult to form single phase of the 2223 phase which shows a critical temperature (a temperature at which the electrical resistance becomes zero) (hereinafter referred to as T.sub.c.sup.zero) of about 110K. Therefore, there are generally known Bi system oxide superconductors utilizing the 2212 phase which shows a low T.sub.c.sup.zero of about 80K but which can be formed in a wide temperature region.
The above Bi system oxide superconductors utilizing the 2212 phase, however, have a problem in that as compared with Y--Ba--Cu--O system (hereinafter referred to as Y system) oxide superconductors, the Bi system oxide superconductors tend to show reduction in critical current density (hereinafter referred to as Jc) when a magnetic field has been applied thereto. Accordingly, the Bi system oxide superconductors are disadvantageous in application to a superconducting electromagnet and a superconducting magnetic shielding material.